The present invention relates to a gas generator for actuating a seat belt pretensioner of an automobile.
A seat belt pretensioner is known as a safety system for protecting occupants in an automobile from an impact generated in a collision of the automobile. The pretensioner is actuated by a large amount of gas introduced by a gas generator and subsequently protects the occupants. The gas generator includes a squib as an ignitor, gas generants and the like. The gas generator ignites the squib in the collision, thereby fires and burns the gas generants then generates a large amount of gas rapidly.
As an example of conventional gas generators, a gas generator shown in FIG. 11 has been proposed. The gas generator shown in FIG. 11 includes a cup body 51 in a shape of cylinder with a bottom loaded with gas generants 52, a tube body 54 housing firing agents 53, and a holder 55 of which some parts are fitted in the cup body 51 and th tube body 54 respectively to seal the cup body 51 containing the gas generants 52 in its inside and the tube body 54 containing the firing agents 53 in its inside. The holder 55 is made of resin. The holder 55 is integrally provided with a squib 56 for igniting the firing agents 53. The squib 56 includes two electrode pins 57, 58 penetrating the holder 55 and projecting within the tube body 54, a bridge wire 59 welded to the respective electrode pins 57, 58 in the tube body 54, and an igniting agent ball 60 covering the bridge wire 59 and being in contact with the firing agents 53.
In this gas generator, the parts of the holder 55 is inserted in an opening of the cup body 51. An end portion of the cup body 51 on the opening side is caulked in caulking groove 63 so that the end portion comes into contact with a sealing ring 61 flexibly in the caulking groove 63 of the holder 55. Thus, the cup body 51 is sealed by the holder 55. Further, an end portion on an opening side or the tube body 54 is supported on the holder 55 by means of an inner cylindrical member 62 fitted in the cap body 51. As a result, the tube body 54 comes into close contact with the holder 55 then an inside space of the tube body 54 is tightly shut out,
In the gas generator of the above-mention d construction, when electric current is passed through the respective electrode pins 57, 58 of the squib 56, the bridge wire 59 generates heat then the igniting agent ball 60 ignites. The igniting agent ball 60 fires the firing agents 53. A flame of ignition of the squib 56 is ejected into the cup body 51. The gas generants 52 are ignited and burned by the flame then a large amount of gas generates rapidly.
However, since this type of conventional gas generator has a construction where the cup body 51 and the holder 55 are sealed by the caulking portion, there is an adverse possibility that a caulking force acts on the holder 55 then the holder 55 is deformed. A lack of high accuracy in the caulking position of the cup body 51 causes direct press and deformation to the holder. The deformation of the holder 55 generates gaps between the holder 55 and the respective electrode pins 57, 58 and the like. Water and the like go into the tube body 54 from the gaps then deteriorate the firing agents 54, the igniting agent ball 60 and the like. Therefore, performance of the gas generator is not ensured over a long period of time of use.
Further, the cup body 51 and the holder 65 are sealed by caulking portion of the cup body 51 and the sealing ring and the like, and the tube body 54 and the holder 55 are sealed by a cup member 62. Therefore, a number of members for sealing the above-mentioned components increases. As a result, cost of manufacture of the gas generators cannot be reduced.
It is an object of the present invention to provide a gas generator for use in occupant safety systems such as seat belt pretensioner, which has excellent durability, and of which cost of manufacture is reduced.
A gas generator comprises a cup body loaded with gas generants generating gas by combustion, a tube body arranged inside of the cup body to contain firing agents ignited by electric current, a holder made of resin and fitted in both the cup body and the tube body for enclosing the gas generants and the firing agents, and a reinforcement is integrated with the resin of the holder by insert molding.
According to the present invention having the above described construction, even when the holder is made of resin, a deformation of the holder caused by a caulking force for connecting the cup body to the holder is restrained by the reinforcement. Also, a deformation of the holder caused by thermal expansion is restrained by the reinforcement.
Therefore, the invention prevents gaps that arise by deformation of the holder, whereby water and the like do not enter the tube body. As a result, performance of the gas generator is ensured over a long period of time of use.
Further, the gas generator of the present invention is preferably constructed as follows. The reinforcement has a protruding portion from an outer periphery of the holder. The protruding portion is fitted into the cup body. Inter-gaps among the cup body, the tube body and the holder are tightly closed by means of a caulking force between the protruding portion and the cup body.
Since the caulking force acts between the cup body and the protruding portion of the reinforcement, high accuracy in the caulking position is not required. Since a simple caulking construction between the cup body and the reinforcement enables the inter-gaps among the cup body, the tube body and the holder to be integrally and tightly closed, the number of sealing members such as sealing rings is decreased. Also, the strength of the holder is increased by the reinforcement. Therefore, a gas generator can be provided, which has excellent durability and for which the cost of manufacturing is reduced.
Additionally, the gas generator of the present invention is preferably constructed as follows. The tube body has a flange protruding towards the cup body, the flange is sandwiched in between the cup body and the protruding portion of the reinforcement.
The reinforcement restrains that the caulking force from acting on the resin of the holder directly, and prevents the holder from deforming.
Also, the gas generator of the present invention is preferably constructed as follows. The reinforcement consists of a cylindrical body and a ring plate body so as to have a cup shape. The cylindrical body protrudes from the outer periphery of the holder. The ring plate body is integrated with the resin of the holder.
The reinforcement constructed above enables the strength of the holder to increase, and the connecting the cup body to the holder with caulking to be done easily.
Another gas generator of the present invention comprises a cup body loaded with gas generants generating gas by combustion, a tube body arranged inside of the cup body to contain firing agents ignited by electric current, a holder made of resin and fitted in both the cup body and the tube body for enclosing the gas generants and the firing agents, and a ring body mounting fixedly on a part of outer periphery of the holder so that an inter-gap between the cup body and the holder is tightly closed.
According to the present invention having the above described construction, high accuracy in a caulking position between the cup body and the holder is not required. The inter-gap between the cup body and the holder is tightly closed by means of a simple operation in which the ring body is mounted fixedly on the part of the outer periphery of the holder.
In addition, according to the present invention, since the caulking force does not act on the cup body directly, the caulking force is restrained from acting on the resin of the holder through the cup body. Deformation of the holder is thereby prevented.
As a result, the cost for manufacturing the gas generator is decreased. Also, the invention prevents gaps from arising due deformation of the holder. Therefore, water and the like do not enter the tube body, the performance of the gas generator is ensured over a long period of time of use. A gas generator can be provided, which has excellent durability and for which the cost of manufacture is reduced.
Further, in the gas generator of the present invention, a sealing layer is preferably provided among the ring body, the cup body and the holder.
The sealing layer improves a seal property among the ring body, the cup body and the holder. As a result, a gas generator with more excellent durability can be provided.